It is probably not your fault. If you are a spammer or
an evil malware distributor, then it is your fault. But in my client's
case, they were trying to send tax forms to their accountant and legal
information to their attorney and their mail was bouncing with the
message above.

Messagelabs was a company that provided various email security
services and was acquired by Symantec in 2008. If you go to the page
referenced in the message it takes you to a rather generic page
http://www.symanteccloud.com/support/ that just gives you contact
information for Symantec Cloud Support. Where you go from here is kind
of a bad news / good news story.

The bad news

Sadly, if you call Symantec they won't do anything for you unless you
are a symantec customer. The customer has to open up a support ticket.

What you have to do is contact whoever you are sending your email to
and get them to call the support number on the page listed above, give
them the IP address of your sending mail server. Symantec will look into
it and eventually remove that IP address from their block list.

Right now, I don't know how long that takes. With some quick
searching on the web, for some it was "A few weeks" and others were
still complaining after months without any resolution. And let me also
note they have a free lookup service and this client's IP addresses were
not listed as having any problems. It has to escalate through
Symantec's tech folks to be resolved.

In my case, we reported it to our client on 3/20/2015 and they
forwarded it to Symantec. It was fixed 3/23/2015 around Noon.

** Do all that first - or at least get it started. It is always
possible Symantec will realize how distruptive they are being to their
customers and make this into an easy, pain-free and fast process that us
end-users can do from a web portal without involving them like almost
every other block list has. It is also possible I will win the lottery
tomorrow, but I'm not betting on that. So gather the information and
have a support case opened up.

The good news

My company specializes in creative problem solving. Even though I can't
fix Symantec, I can find a creative way to get the mail through.

Your free work around: Send the mails to another free email service -
like gmail, or hotmail, or yahoo... and then forward it onto your
destination. It is a pain in the ass, but it is a solution that will get
a stray email or two through in a pinch.

If you have more than one or two users - or perhaps your entire
company is being blocked - and the free work around isn't practical, I
offer a service that will work around the problem for you. I can have
everything setup in under an hour. Contact me at the 'Contact Us' link
at the top left of this page for more details.

If you hit this and have some data on 'how long it took for Symantec
to fix this' in your case, I would love to hear about it.